CHILD LANGUAGE

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CHILD LANGUAGE
Acquisition of speech sounds,
segmenting the phonetic string
The target
• Arbitrary relationship between sound and
meaning
• Abstract concepts, displacement from here
and now
• Hierarchical organisation, compositionality:
sounds-words-(phrases)-clauses-sentencestext
• Astronomical (perhaps infinite) number of
form-meaning pairings
The target
• Sketchiness: only some of the intended meaning is expressed
explicitly, the rest has to be inferred by the listener
– Done.
• Ambiguity: words, structures, whole sentences may be
ambiguous – relevant meaning needs to be recovered from
context
– Drunk gets nine months in violin case (Pinker 1984)
• Cultural embeddedness: communication requires implicit
understanding of the intentions of conversation partners,
social habits
– She had her leg waxed vs. She had her leg broken
• Transmissibility: messages are transmitted rapidly and
relatively errorlessly – processing is done on-line using a
variety of sources of information
The input
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Varies across cultures
No systematic instruction in most cultures
Teaching at best through correction of errors
Syntactic rules are never explained, most
people are not aware of them
Speech sounds
• Set of acoustic cues identify speech sounds
• They are influenced by:
– Neighbouring sounds
– Overall utterance prosody
– Speech rate
– Speaker voice quality
– Environmental noise, etc.
Phonemes and allophones
• Phoneme: speech sounds that distinguish
words (sinner vs. singer)
• Allophones: phonetically different speech
sounds that do not distinguish words (enged)
• Every language has its own phoneme
inventory
• Categorical perception: we cannot hear
“meaningless” differences in sounds. Sounds
are automatically categorised.
19th century
Headturn
preference
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Head-turn preference paradigm
Light from left or right
Auditory stimulus from same area
Length of looking measured
Results of experiments: language discrimination
• Newborns can distinguish their native language from other
languages of a different rhythm (Mehler et al 1988)
• They can also discriminate between two unfamiliar
languages of different rhythms (Mehler & Christophe 1998,
Nazzi et al 1998)
• But at 2 months of age they stop discriminating between
unfamiliar languages (Mehler et al 1988, Christophe &
Morton 1998)
• In the first few months discrimination is based on rhythm
and intonation
• At 5 months, infants can also rely on individual speech
sounds (they can distinguish languages with similar
intonation patterns, such as Dutch and English) (Nazzi et al
2000)
• By 9 months, infants prefer to listen to
unknown words not violating the phonotactic
patterns of their language (e.g., pottle vs.
tlepen)
• They also prefer nonsense words with
frequent sound combinations
Results of experiments: phoneme discrimination
• Categorical perception at 1 month of age (Eimas
1975)
• Confirmed by ERP studies: odd-ball detection
paradigm (electrophysical response to novel
auditory stimulus) (Cheour-Luhtanen et al 1995)
• For the first few months, infants can distinguish
phonemes in any language, but by age 6-8
months, they are only sensitive to contrasts in
their native language (Kuhl et al 2006)
• At 9 months, infants can re-learn to
discriminate phonemic contrasts in foreign
languages (Kuhl et al 2003)
– after twelve 25 minute reading sessions
Kuhl: The linguistic genious of babies
http://www.youtube.com/watch?v=G2XBIkHW954
Possible learning mechanisms
• Top-down from word meaning: phonemes distinguish
words
– But 10 month-olds have a very small vocabulary
• Distributional learning:
– non-contrastive sound pairs (allophones) occur in
complementary distribution – e.g. English vowel
nasalisation
– systematic phonetic variation which is not contextually
predictable is contrastive in the target language
• Categories influence perception: items in the same
category are perceived to be more similar than items
across category boundaries
Segmentation
• There are no universal syllables
• Languages differ widely in their rhythmic
structure
• Only subtle cues to word boundaries (segment
duration, allophonic variation, phonotactics), but
they are neither obvious nor universal
• Segmentation errors are common in adult speech
processing
• Top-down processes seem to play a major role for
adults
whereare the s
Saffran 2003
ilen
ces
betw
eenwor
d
s
Distributional evidence
• Transitional probabilities
• pretty baby, pretty dress, pretty doll
-> pre+ty highly probable (within word), ty+ba less probable (across word
boundaries)
• Nonsense language learning experiments (Saffran et al 1996, Aslin,
Saffran & Newport, 1998):
In training phase 8 month-olds listen to uninterrupted sequence of 3syllable words: bidakupadotigolabubidaku
In test phase they listen longer to nonwords (kupado) than to words
(bidaku)
• Works with musical notes (Saffran, Johnson, Aslin & Newport 1999)
• Tamarin monkeys are as sensitive as human children (Hauser,
Newport & Aslin, 2001)
• Infants under 6 months cannot reliably identify these word
segments
Statistical learning
• Implicit, procedural learning of probabilistic
co-occurrence patterns
• based on invariance detection through
attention to relatively stable patterns or
regularities (Gogate & Hollich 2010)
Prosodic properties as cues
• Noise detection experiments
6 month-olds are slower to detect noise if it interrupts two-syllable
sequences with typical stress pattern (Morgan 1996)
• 9 month-olds prefer words with typical stress pattern
(Jusczyk 1997, 1999, 2002)
• they listened to isolated words with typical (kingdom, hamlet)
vs. atypical (device, align) stress pattern
• then they listened to passages with or without the test words
• they listened longer to passages with the typical words
• Frequency of sounds varies by environment: word initial,
word medial, across word boundaries. 9 month-olds are
sensitive to these patterns (Mattys & Jusczyk 2001, Brent &
Cartwright 1996)
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